Additives useful in preparing spinning dopes of spandex type polymers



United States Patent US. Cl. 260-75 14 Claims ABSTRACT OF THE DISCLOSURE An extrudable dope for preparing spandex articles, such as fibers, comprising a solution of a spandex type polymer containing a fl-diketone, the ,B-diketone functioning to inhibit undesirable side reactions during preparation of the dope, during storage of the dope and while extruding fibers, films, or the like, from the dope. Suitable fl-diketones have the formulas:

and

wherein R', R", and --R"' comprise organic radicals of between 1 and 25 carbon atoms consisting essentially of carbon and hydrogen atoms or such atoms in combination with from 1 to 6 hetero S or O atoms separated from carbonyl in the formulas by at least one intervening carbon atom.

This invention relates to an improved extrudable dope that comprises a spandex type polymer and, in addition, relates to a method of inhibiting undesirable side reactions at various steps in the formation of such an extrudable dope, as well as during its storage.

By a spandex type polymer, We mean a polymer formed from a substantially linear, segmented elastomeric material. The words substantially linear are not intended to exclude structures having branches extending out from the polymer chain, but exclude only those structures which are highly cross-linked. The words segmented elastomer mean that the elastomer under consideration has segments of'a high melting point crystalline polymer, that is, hard segments, that alternate with segments of a low melting point, amorphous polymer, that is, soft segments.

Extrudable dopes such as spinning dopes are well known andwidely used in industry for the manufacture of many different types of products. An extrudable dope of a spandex type polymer comprises the combination of the spandex type polymer and a solvent medium, the polymer having been substantially dissolved in the solvent to provide a relatively viscous liquid material. Such spinning dopes may be utilized in the manufacture of textile fibers by spinning or extruding the spandex dope through a plurality of spinneret orifices, thereby producing stretch textile fibers. Also, such extrudable dopes may be used in the manufacture of sheeting materials by extruding the dope through a suitable extrusion die, thereby forming elastic sheeting. In addition, such extrudable dopes may be utilized for coatings of various substrate by depositing on the substrate a regulated thickness of the dope, the coating thickness being regulated by means of, for example, a doctor blade. In all cases, however, the dope must be subjected to some type of curing means once it exits from the spinneret orifice, or

3,506,620 Patented Apr. 14, 1970 the extruder die, or is deposited on the substrate. The curing medium operates to evaporate the solvent from the spandex polymer, thereby leaving the polymer in the configuration and form so desired.

Generally, and as is well known in the art, spandex type polymers, and extrudable dopes thereof, are produced by first creating the spandex prepolymer. The spandex prepolymer is typically prepared by reacting a polymeric glycol such as a polyether glycol, copolyether glycol, polyester glycol, copolyester glycol, or poly(etherester) glycol, denoted as G in the equations below, with a stoichiometric excess of an isocyanate, denoted as I in the equations below. An excess of isocyanate is normally used to ensure that an isocyanate capped prepolymer, that is, an intermediate product whose polymer chains are tenninated with isocyanate groups, is produced. The prepolymer reaction proceeds substantially as follows, although it will be understood that the resulting prepolymer obtained actually constitutes a conglomeration of monomer, polymer, oligomer, and unreacted isocyanate:

wherein n represents 0, 1, 2, 3, and so on to give the conglomerate mixture. The difunctional prepolymer is then generally placed in a solvent medium, particularly if textile fibers, sheeting, or film coatings are to be the final product.

A difunctional chain extender, for example, water or any of numerous diamine chain extenders known to the art, is then added to the prepolymer solution when it is desired to chain extend the prepolymer. Sufiicient chain extender is added to the prepolymer solution to ensure that substantially all isocyanate groups react, thereby chain extending the prepolymer and forming the final spandex polymer. The following generaly equation, wherein D represents the amine groups, schematically represents the chain extension of a spandex prepolymer:

Because the spandex prepolymer is normally chain extended while a suitable solvent medium, the spandex dope so formed may then easily be spun, by either wet or dry spinning techniques, into textile fibers, or extruded into sheeting materials, or cast into coatings, and so forth, of the spandex polymer.

During manufacture of spinning dopes, as just described, the prepolymer may be stored in the solvent medium until it is needed for end product manufacture, at which time the prepolymer is subjected to chain extension to form the final spinning dope of the spandex type polymer just prior to its use. Alternatively, after the prepolymer has been solutionized it may be subjected to chain extension to form the final spinning dope, and the spinning dope itself may then be stored until it is required for production use.

However, because of the unique nature and chemistry of spandex type polymers, the preparation and storage of spinning dopes of spandex polymers gives rise to a number of problems which need to be resolved if the practical and commercial utilization of spandex polymers is to be widely received. Such problems may occur during either the prepolymer or the chain extension stage in preparing spinning dopes of spandex type polymers, and these problems are normally increased and accentuated during storage of both the prepolymer solution and the final spinning dope.

With regard to the preparation of the spandex prepolymer, it is hypothesized that certain types of side reactions may occur during preparation of the prepolymer which lead to the formation of gel particles during subsequent preparation and reaction steps. For example, after the ice prepolymer has been formed, there is normally a residual amount of diisocyanate left in the reaction pot. It is oftentimes desirable to remove this diisocyanate from the pot by heating the diisocyanate under reduced pressure, but this step often promotes the undesirable side reactions in the prepolymer. The effect of undesirable side reactions during production of the prepolymer creates problems, such as, for example, gel formation, during the subsequent chain extension step of the process.

Various undesired side reactions may occur; for example, isocyanate groups on the prepolymer may react with urethane linkages present in the prepolymer, or with each other, to form undesirable uretidione or isocyanurate groups.

Once the prepolymer has been formed it is generaly introduced into a solvent medium and may be so stored in this state, as mentioned above. However, the prepolymer solution is not indefinitely stable as storage of the prepolymer solution permits the undesirable side reactions mentioned to continue, thereby accentuating the gelation problem and low molecular weight problem upon chain extension of the prepolymer.

With regard to the chain extension step in forming the spandex polymer and, simultaneous therewith, the final spinning dope, it is not uncommon to have gelation occur during chain extension of the prepolymer to an extent that makes the dope unsuitable as a spinning dope in creating end products. Spinning of such gelled dopes has been found very difficult because the dope tends to plug filters as well as spinnerets and/ or dies in the formation of end products. Of course, once the spinning apparatus starts to become plugged the spinning pressures rise, and the apparatus and process must be stopped to permit cleaning of the equipment. Also, the products formed from such nonhomogeneous dopes are themselves nonuniform, for example, fibers will have considerable denier variation and will be unacceptable from a retailers and consumers standpoint.

Also, it is hypothesized that the isocyanate groups on the prepolymer and/ or final polymer may react with components of the final dopes solvent system, in addition to the previous side reactions mentioned, to terminate the polymer chains when certain types of desirable solvents are used. This, of course, lowers the concentration of free isocyanate groups susceptible to reaction during the chain extension step as well as during any post formation treatment that may be used to increase the total polymer molecular weight. This loss of isocyanate groups on the prepolymer causes a spandex polymer of a lower molecular weight to be formed upon chain extension of the prepolymer. A low molecular weight polymer causes a spandex product with lower end product physical properties to be produced.

Another problem that often occurs during chain extension of the prepolymer into final spinning dope form is a phenomenon known as stirrer shaft climbing. This phenomenon is, in essence, a practical problem arising from the presence of gel particles caused by the undesirable side reactions when forming the prepolymer. During chain extension of the prepolymer, the reactants and products often have an excessive tendency to climb the stirrer shaft even at low solution viscosities. It is obvious that this creates processing ditficulties and makes it difficult to prepare a dope at a suitable viscosity for subsequent product formation. In addition, such dopes are generally nonhomogeneous, thereby adding to the problems encountered in product formation.

Also, because of the stirrer shaft climbing phenomenon and the poor mixing caused thereby, less than the desirable amount of chain extender can be used to the prepolymer solution. Generally, when a spinning dope begins climbing the stirrer shaft continuous addition of the chain extender only makes gelation, and stirrer shaft Climbing, more prominent with the result that the spinning dope ultimately becomes relatively unprocessable, On the other hand, if less chain extender is added during chain extension of the prepolymer to combat this problem, the resulting product will contain a lesser number of urea groups than when more chain extender is added. The urea groups or high melting segments provide an essential part of polyurethane elastomers in that they are necessary tie down points between polymer molecule chains.

The solution, of the chain extended spandex polymer, that is, the final spinning dope, is more unstable than the prepolymer solution, and accordingly, the storage problems which occur in connection with the prepolymer solution are compounded and increased when a spinning dope is stored. That is, the longer a spinning dope is stored the worse its processability becomes because of the factors noted above.

It has been found that the above mentioned problems in the formulation of spandex polymer dopes largely arise from the presence of impurities in the reactant system. Such impurities include metal compounds, in trace amounts or greater, and include compounds of iron, cobalt, lead, zinc, bismuth, and others. Such metal compounds appear to strongly catalyze the undesirable side reactions during preparation of the spinning dope. Of course, it is almost impossible to create spandex dope formulations, from a practical or commercial standpoint, in environments which are completely free of metals. The creation of dopes normally takes place in reaction vessels formed of metals and trace metal impurities are often garnered from this source. This application is based on the inventive concept of a composition of matter, that is, a spinning dope, that comprises a spandex type polymer and a {i-diketone. The B-diketones have been unexpecedly and surprisingly found to inhibit the catalytic action of trace metal impurities that are often found in polymer formulation systems, thereby alleviating problems encountered with gel formation and stirrer shaft climbing. In addition, the inventive concept is based on an improved method of inhibiting side reactions durng preparation and storage of prepolymer solutions and spinning dopes which includes the step of incorporating a fi-diketone in for example, the prepolymer solution prior to storage.

Thus, it has been the primary objective of this invention to provide an additive for both a spandex prepolymer solution and a spandex spinning dope which function to inhibit the formation of gel particles in the final spinning dope.

It has been another objective of this invention to provide a method of creating a smooth, substantially gel free, spandex spinning dope, thereby retarding stirrer shaft climbing, and providing a relatively easily processable dope that creates relatively few equipment plugging problems.

It has been yet another objective of this invention to retard adverse and undesirable side reactions that may occur in either the prepolymer preparation, the prepolymer solution or the final spinning dope.

It has been still another objective of this invention to prevent the premature terminal of the spandex polymer chains by preventing undesirable side reactions that tend to reduce the amount of isocyanate groups on both the prepolymer and the final polymer.

Other objectives and advantages of this invention will be more apparent to those skilled in the art from the following detailed description in conjunction with the accompanying drawing in which the figure graphically illustrates the reduction in isocyanate group loss of a spandex prepolymer solution utilizing this invention.

While the inventive concept of this application may be used with spinning dopes formulated from substantially any spandex type polymer, it is particularly useful and preferred for use with certain type of spandex polymers disposed in U.S. application Ser. No. 379,002, filed June 29, 1964, and now abandoned; 379,020, filed June 29, 1964, and now abandoned; 378,950, filed June 29, 1964, and now abandoned; 378,961, filed June 29, 1964, and

now abandoned; 378,963, filed June 29, 1964, and now U.S. Patent No. 3,386,942, issued June 4, 1968. Such polymers may be prepared and produced as spinning solutions or dopes according to methods set forth in U.S. application Ser. No. 378,951, filed June 29, 1964, and now abandoned and 378,711, filed June 29, 1964, and now U.S. Patent No. 3,415,790, issued Dec. 12, 1968, all the aforementioned applications having been assigned to the assignee of this application. For example, a spinning dope comprising the spandex polymer disclosed in US. application Ser. No. 379,002 filed July 29, 1964, and now abandoned is very beneficially affected by incorporating the additives of this invention and it comprises a poly (ether-urethane-urea) composed of 1) polyethers including urethane linked oligomers thereof having a molecular weight of from about 3,000 to about 12,000, (2) organic functionally aliphatic diisocyanates, and (3) water and/or organic functionally non-hindered diamines, in which segmented copolymers from 2% to 9% by weight consist of urea segments. These substantially linear, segmented elastomers, where the urea segment is composed of a single repeat unit, can be represented by the general formula:

wherein the urea or hard segment has the formula:

-A-NHCONH-DNH-CO-NH and the soft segment, which contains the polyether glycol or other hydroxyl terminated polymeric residue, has the formula:

The A- and -D- radicals may be different or the same in each repeat unit of the above formulas. The A radical is the bivalent organic radical of a functionally aliphatic diisocyanate having the formula:

and the D- radical is the bivalent organic radical of a functionally aliphatic, non-hindered diamine having the formula: N1-l -DNH Hydrazine can also be employed as such a diamine. The --P- radical is the bivalent organic radical of a polyether glycol having the formula: HOPOH. The polyether glycol may be replaced with a polyester glycol or a poly(ester-ether) glycol of analogous properties and also being represented by the formula: HO-P-O'H. This formula is intended to also encompass oligomers as explained above.

As mentioned, part of the inventive concept of this invention includes a composition of matter comprising a spandex type polymer and a ,B-diketone. Suitable B-diketones which are useful include those of the general formulas:

wherein R', R", and -R"' comprise organic radicals of between one and twenty-five carbon atoms. The organic radicals may be of aliphatic, cycloaliphatic, aromatic, or arylalkyl types. Advantageously such radicals contain carbon and hydrogen and may also contain halogen in place of hydrogen. Such radicals may also contain heteroatoms, for example, S or -O, heteroatoms which are separated from the carbonyls of the diketone by an intervening carbon atom.

Suitable aliphatic p-diketones include 2,4-pentanedione; 2,4-hexanedione; 2,4-undecanedione; 3,5-heptanedione; 3-ethyl-2,4-pentanedione; 3-octyl-2,4-pentanedione;

l-phenyl-l,3-butanedione; 1-benzyl-1,3-butanedione; 1- cyclohexyl-1,3-butanedione; 1-furyl-1,3-butanedione; lmethoxy-2,4-pentanedione; l-thenyl-1,3-butanedione; 1-

6 phenyl-2-n-butyl-1,3-butanedione; 1 phenyl-2-ethyl-l,3- butanedione; 1phenyl-2-n-heptyl-1,3-butanedioue; 2,2-dirnethyl-4-e-thyl-3,S-hexanedione; 2,2 dimethyl-4-benzyl- 3,5-hexanedione; 2,2-dimethyl-4-n-butyl-3,S-hexanedione; dipi'valoylmethane; hexafiuoroacetylacetone and trifluoroacetylacetone.

Suitable cycloaliphatic fi-diketones include l-cyclohexyl-1,3-butanedione.

Suitable arylalkyl ,B-diketones include 1-benzyl-1,3-butanedione; 1-furyl-1,3-butanedione; 1-phenyl-2-benzyl-1, B-butanedione; and 2,2-dimethyl-4-benzyl-3,S-hexanedione.

Suitable aromatic fl-diketones include 1-phenyl-1,3-butanedione; 1-furyl-1,3-butanedione; 1-thenyl-1,3-butanedione; l-phenyl-Z-n-butyl-1,3-butanedione; 1 phenyl-Z- ethyl-1,3-butanedione; 1 phenyl-Z-n-heptyl-1,3-butanedione; l-phenyl-Z-benzyl-1,3-butanedione; dibenzoylmethane; and dinaphthoylmethane.

Suitable fi-diketones which include heteroatoms include 1-furyl-1,3-butanedione; 1methoxy-2,4-pentanedione; and l-tetrahydrofuryl-1,3-butanedione wherein the heteroatom is O-; l-thenyl-1,3-butanedione; and thenoyltrifluoroacetone wherein the heteroatom is -S.

It has been found necessary to add the fl-diketone in an amount between about 0.0005 and about 5.0% by weight, based on the weight of the polymer. It is preferred in most commercial circumstances, however, to utilize an amount of fi-diketone from about 0.002% to about 2.0% by Weight for reasons of economy.

Thus, the spinning dope composition of this invention surprisingly has been found to provide smooth, homogeneous dopes that are substantially free of gel particle formation, thereby permitting the dopes to be spun into fibers for long periods of time without stopping the process. In addition the spinning dope composition substantially retards and prevents undesirable side reactions usually catalyzed by metal impurities, thereby preventing premature termination of the spandex molecules and permitting the achievement of optimum physical properties in the spandex fiber.

A preferred method of this invention includes the step of incorporating the ,B-diketone additive during the prepolymer formulation step, that is, while the prepolymer is being created. By incorporating the additive during the creation of the prepolymer, a thorough and intimate admixture is achieved. Thus, the additive may perform its function of inhibiting and retarding side reactions, as well as promoting storage life, at optimum efliciency. Alternativetly, the fi-diketone may be incorporated after the prepolymer has been substantially solutionized with a suitable solvent medium. It is preferred to incorporate the ,B-diketone additive at either of these points, namely, during creation of the prepolymer or after the prepolymer has been placed in solution, because it is preferred to store the prepolymer solution, as opposed to the final spinning dope itself. As a general rule, the prepolymer solution has a longer storage life than the spinning dope.

As mentioned, the prepolymer in the solvent medium may be chain extended prior to storage, thereby formulating the final spinning dope. In this case the spinning dope itself, as opposed to the prepolymer solution, would be stored. If this alternative mode of operation is followed, the additive may be incorporated with the spinning dope prior to, during, or just after the prepolymer is chain extended if it has not been previously so incorporated.

The incorporation of a ,B-diketone additive with a prepolymer solution has been found to lengthen the storage or shelf life of such a solution twofold or more. On the other hand, because a spinning dope is inherently more unstable than a prepolymer solution, the incorporation of a ,B-diketone additive with a spinning dope has been found to increase the storage life of the dope ten-fold or more.

As is apparent from the above description, one aspect of this invention provides a composition of matter comprising a spandex polymer, a solvent medium for said spandex polymer, and a B-diketone.

According to another aspect of this invention there is provided such a composition wherein the spandex polymer is an elastomeric segmented copolymer of (1) a polymeric glycol having a molecular weight of from about 600 to about 12,000, urethane linked oligomers of a polymeric glycol, or combinations thereof, (2) a molar excess of an organic diisocyanate and (3) as a chain extender, water, hydrazine, a dihydrazide, an organic diamine or combinations thereof.

According to a further aspect of this invention there is provided a composition of matter comprising a prepolymer of a polymeric glycol and a molar excess of an organic diisocyanate, and a fi-diketone.

The following examples serve to illustrate our invention; however, they are included merely for the purpose of illustration, and not for the purpose of limiting the scope of the inventive concept as claimed. All percentages used in the following examples are expressed in percent by weight unless otherwise specified.

EXAMPLE I An isocyanate terminated prepolymer solution is prepared. The isocyanate terminated prepolymer is present in a solvent medium composed of methylene chloride, tert-butyl alcohol, and N,N-dimethylacetamide. Four different portions of the prepolymer solution are selected. Portion 1 represents the control wherein no fl-diketone is added, it being thought that the control is substantially free from impurities and the like. To portions 2 and 3 are added 1.5 p.p.m. of Fe+ in the form of ferrous chloride. To portion 3 is added 0.0009% (based on the prepolymer weight) of a p-diketone, namely 2,4-pentanedione, in addition to the ferrous chloride. To portion 4 is added 1.0% of 2,4-pentanedione. Thus, the control portion, that is, portion 1, contains no additive; portion 2 contains only Fe+ which is known to promote undesirable side reactions that use up free isocyanate groups; portion 3 contains Fe+ and 2,4-pentanedione, that is, the additive of this invention; and portion 4 contains only 2,4-pentanedione.

The percent isocyanate on the prepolymer that takes part in undesirable side reactions, thereby depleting the free isocyanate group supply for chain extension, is determined in each case by nuclear magnetic resonance measurements at different times subsequent to the original formulation of the prepolymer solution. The results are graphically illustrated in FIGURE 1 and they depict the rate of isocyanate loss is the 35 C. prepolymer solution.

It may readily be seen from the figure that the addition of the B-diketone drastically reduces the percentage of isocyanate loss, upon standing, in the prepolymer solu tion when metal compounds are present in the solution. It may also be seen from the graph that the loss rate of isocyanate groups from the prepolymer solution with only the fl-diketone is substantially less than that of the prepolymer solution with no fi-diketone additive or metal compound. Thus, the fi-diketone inhibits undesirable side reactions caused by unknown impurities that are almost always present in prepolymer solutions.

EXAMPLE II A number of different polymeric glycols are prepared with 0.010% to 0.015% (based on expected prepolymer weight) 2,4-pentanedione being added to the polymeric glycol as the [i-diketone additive. Subsequently, the polymeric glycol, with the fi-diketone additive, is reacted with an organic diisocyanate to form seven different prepolymers. The different prepolymers are then each chain extended with a diamine.

As a reference point, for good processability it is commercially desirable to have a spinning dope with a viscosity of about 200 to about 400 poises at 35 C.

It will be noted from the table below that when no fl-diketone is utilized the spinning dope exhibits the phenomenon of stirrer shaft climbing, even at relatively low diamine addition percentages, and is unacceptable from a commercial standpoint in regard to dope viscosity. On the other hand, when a fl-diketone is utilized in the formulation of a spinning dope, the diamine percentages which may be utilized can be increased, thereby permitting a better end product to be produced; no stirrer shaft climbing is observed; and the viscosity falls well within the range for good dope processability.

TABLE 1 Spinning (lope characteristics B-Diketone Diamine added, climbs viscosity, poises present percent stirrer at 35 C 85.5 Yes 172 153 295 310 295 EXAMPLE 'III (A) A copolyether glycol of 4,700 molecular weight is prepared from tetrahydrofuran and 8-0xabicyclo[4.3.0l] nonane, and contains 7.7 mole percent of the latter, as described in US. application Ser. No. 231,588, filed Oct. 18, 1962, and now abandoned, A prepolymer is prepared by reacting 922 gm. of the anhydrous glycol with 73.7 gm. of p-xylylene diisocyanate for 4.5 hr. while stirring under nitrogen. During preparation of the prepolymer, 0.01% (based on expected prepolymer weight) 2,4- pentanedione is added to the copolyether glycol. The prepolymer is then extracted three times by using three volumes of anhydrous acetonitrile per gram of prepolymer to remove unreacted p-xylylene diisocyanate, as described in US. application Ser. No. 378,711, filed June 29, 1964, and now US. Patent No. 3,415,790, issued Dec. 10, 1968. The extracted prepolymer has a diisocyanate analysis of 1.91% (calculated as p-xylylene diisocyanate).

The extracted prepolymer, in an amount of 249.0 gm., is then dissolved in 1,003 gm. of methylene chloride that contains 1.54 gm. of hexamethylphosphortriamide, and the temperature of the solution is raised to 38.5 C. After adding 325 gm. of tert-butyl alcohol to the prepolymer solution, there is then added a solution of 2.72 gm. (92.5% of that amount theoretically required to achieve 100% chain extension) of 1,6-hexanediamine in 272 ml. of tertbutyl alcohol with vigorous stirring to the prepolymer solution over a period of 14 min. As antioxidants, 2.5 gm. of dilauryl-3,3'-thiodipropionate and 5.0 gm. of 2,6-didodecyl-p-cresol are added to the dope. Acetic anhydride, in an amount of 1.3 ml. is added to prevent further molecular chain buildup and 0.025 g. of 2,4-pentanedione is added.

The spinning dope so prepared is found to have a viscosity of 560 poises at 38 C. No climbing of the stirrcr shaft by the dope, during its preparation, is observed.

The spinning dope is then spun or extruded through spinnerets, by dry spinning techniques, into spandex textile fibers. Spinning of the dope proceeds very smoothly. There is no plugging of spinneret holes and the spinning pressures remain substantially constant. Visual inspection of the dope shows it to be smooth and homogeneous with substantially no gel formation.

(B) A spinning dope is prepared in the exact manner as is the dope in part (A) of this example except that no fl-diketone is added to the copolyether glycol.

The dope so formed is found to have a viscosity of only 100 poises at 38 C. Spinning of the dope, by dry spinning techniques, is found to be difficult due to repeated plugging of the spinneret holes. The spinning pressures increase about 640 p.s.i. during a 12 min. period.

9 Visual inspection of the dope shows it to contain a good deal of gel formation.

EXAMPLE IV (A) A prepolymer is prepared by the procedure noted in Example III; however, the diisocyanate is not removed. 2,4-pentanedione is added to the prepolymer solution in an amount equal to 0.015% based on prepolymer 1 weight, The prepolymer is dissolved in a solution of N,N- dimethylacetamide and then chain extended with 1,8- methanediamine to give a spinning dope of 12% solids.

Stirrer shaft climbing is not observed during dope preparation. The dope so prepared has a viscosity of 300 poises at 38 C., is of a smooth consistency, and is substantially free of gel particles. The spinning dope is then spun into spandex textile fibers by wet spinning techniques, that is, by spinning the dope into a 60 C. water bath. No difiiculty is encountered during spinning due to plugging of spinneret holes.

(B) A spinning dope is prepared in the exact manner as is the dope in part (A) of this example except that no p-diketone is added to the prepolymer solution.

Spinning of the dope, by wet spinning techniques, is found to be most difficu-lt due to repeated plugging of spinneret holes. Visual inspection of the dope shows it to contain a good deal of gel formation.

EXAMPLE V (A) A diiferent prepolymer is prepared by reacting 2 mole parts of 4,4-diphenylmethane diisocyanate with one mole part of a 2,000 molecular weight polyester glycol, the glycol having been prepared from adipic acid and ethylene glycol. The prepolymer is dissolved in N,N-dimethylformamide and 0.015% (based on prepolymer weight) of 2,4-pentanedione is added to the prepolymer solution.

The prepolymer solution is then chain extended with 4,4-diphenyl-methanediamine to give a final spinning dope of about 16 weight percent solids.

The spinning dope so prepared is smooth and homogeneous with a viscosity of 200 poises at 29 C. The dope is easily spun into uniform textile fibers which exhibit commercially acceptable physical properties.

(B) Another prepolymer is prepared in the exact manner as is the dope in part (A) of this example except that no fl-diketone is added to the prepolymer solution.

The dope so prepared has a viscosity of only 120 poises at 28 C. and contains many gel particles. The dope is difiicult to spin into fibers as repeated plugg ng of spinneret holes occurs.

EXAMPLE VI (A) A copolyether glycol is prepared from tetrahydrofuran and 8-oxa'bicyclo [4.3.0] nonane by the procedure noted in Example III. The polyether glycol has a molecular weight of 4,300 and contains 6.3 mole percent of the nonane. The glycol is dissolved in cyclohexane and extracted three times with a mixture of 75% methanol and 25% water. After extraction the copolyether glycol has a molecular weight of about 4,800.

A prepolymer is then prepared by reacting 150 lb. of the extracted anhydrous copolyether, containing 10.2 gm. of 2,4-pentane dione, with 13.2 lb. of p-xylylene diisocyanate, the diisocyanate being dissolved in 23.1 lb. of toluene, for hr. while stirring under nitrogen at 95 C. Unreacted p-xylylene diisocyanate is stripped in a thin film evaporator at 100 C. and 400900 microns of pressure by a procedure described in U.S. application Ser. No. 378,711, filed June 29, 1964, and now US. Patent No. 3,415,790, issued Dec. 10, 1968. The stripped prepolymer has an analysis of about 2.28% diisocyanate, calculated as p-xylylene diisocyanate.

A sample of the stripped prepolymer, in the amount of 471 gm., is dissolved in 1,795 gm. of methylene chloride that contains 4.79 gm. of hexamethylphosphortriamide.

To this solution is added 543 gm. of a solution consisting of 90% tert-bntyl alcohol and 10% methylene chloride. Whi-le vigorously stirring the prepolymer solution, 91% of the theoretical amount required to effect complete chain extension, that is, 7.4 gm. of 1,4-cyclohexanebis- (methylamine) dissolved in a solution consisting of 720 ml. of 90% tert-butyl alcohol and 10% methylene chloride, is added over a period of 27 min. A spinning dope results to which is added 9.58 gm. of 2,6-didodecyl-pcresol, 4.79 gm. of dilauryl-3,3-thiodipropionate as antioxidants; 0.0479 gm. of 2,4-pentanedione, as the ,B-diketone; and 2.4 gm. of acetic anhydride to prevent further increase in dope viscosity.

The dope so produced has a viscosity of 240 poises at 27 C. and is smooth with no gel particles present. The dope is subsequently spun, utilizing dry spinning techniques, with no difificulty into textile fibers of commercially acceptable physical properties.

(B) Example V1 is repeated using the fi-diketones tabulated in Table 2 in place of 2,4-pentanedione used in part (A) of this example. The spinning characteristics of the dopes, as they are spun into fibers, are indicated in the table.

*0-50 p.s.i. increase per hour.

EXAMPLE VII Another series of spinning dopes are made according to the procedure set forth in Example VI(A) with various B-diketones being utilized. Each of the dopes with a ,B-diketone additive is spun into textile fibers and similar dopes, without the fi-diketone additives, are also spun into fibers for comparison purposes. The finished fibers are permitted to age 2 weeks at 50% relative humidity. The inherent viscosity of the finished textile fibers then is measured and is tabluated in Table 3.

Inherent viscosity as used herein, is defined as In N /C. N represents the viscosity of a spandex polymer solution at 25 C. (the solvent comprises 60% phenol and 40% tetrachloroethane) divided by the viscosity of the solvent alone at 25 C. C represents the concentration of the spandex polymer in gm./ ml. of solution. A concentration of about 0.02 to 0.5 gm./l00 ml. of solution is normally used. The notation insoluble in Table 3 means that the particular polymer had such high molecular weight that it was insoluble in the solvent and for the tests and therefore its I.V. could not be measured.

'I'ABLE 3 fi-diketone: Fiber inherent viscosity 2,4-pentanedione 6.53 None 4.99 2,4-pentanedione 6.66 None 5.60 3,5-heptanedione Insoluble None 4.81 3-octyl-2,4-pentanedione 6.50 None 4.25 1-phenyl-l,3-butanedione insoluble None 6.00

The above examples illustrate the usefulness of using ,B-diketones to reduce or substantially eliminate side reactions which cause polymer chain termination during preparation of the spinning dope. This makes quite feasible the formation of unusually high molecular weight spandex polymers with excellent elastomeric properties. It can be quite desirable to have an unusually high inherent viscosity which is directly related to the molecular weight of the spandex polymers. In general it can be said that the higher the inherent viscosity, the higher will be the polymer molecular weight and the better will be the fibers physical properties.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention as described hereinbefore and as defined in the appended claims.

We claim:

1. A composition of matter comprising a substantially linear, elastomeric, fiber-forming, long chain copolymer, a solvent medium for said copolymer, and a B-diketone.

2. A composition of matter as set forth in claim 1 wherein said fl-diketone is selected from the group consisting of o o R tain-G 3 and o R-iion" R R wherein -R', R", and R'" comprise organic radicals of between 1 and 25 carbon atoms consisting essentially of carbon and hydrogen atoms or such atoms in combination with from 1 to 6 hetero S or O atoms separated from the carbonyl in the formulas by at least one intervening carbon atom.

3. A composition of matter as set forth in claim 2 wherein said organic radicals are selected from the group consisting of aliphatic, cycloaliphatic, arylalkyl, and aromatic radicals.

4. A composition of matter as set forth in claim 2 wherein said organic radicals contain a heteroatom, said heteroatom being joined to said fi-diketone through at least one carbon atom.

5. A composition of matter as set forth in claim 1 wherein said fi-diketone is present in an amount between about 0.0005% and about 5.0% by weight based on the weight of the copolymer.

6. A composition of matter as set forth in claim 1 wherein said fi-diketone is present in an amount of between about 0.002% and about 0.2% by weight based on the weight of the copolymer.

7. A composition of matter as set forth in claim 1 wherein the copolymer is an elastomeric segmented copolymer of (l) a polymeric glycol having a molecular weight of from about 600 to about 12,000, urethane linked oligomers of polymeric glycol, or combinations thereof, (2) a molar excess of an organic diisocyanate and (3) as a chain extender, Water, hydrazine, a dihydrazide, an organic diamine or combinations thereof.

8. A composition of matter comprising a prepolymer of a polymeric glycol and a molar excess of an organic diisocyanate, and a fl-diketone.

9. A composition of matter as set forth in claim 8 including a solvent medium for said prepolymer.

10. A composition of matter as set forth in claim 8 wherein said fl-diketone is selected from the group consisting of wherein R, R", and R comprise organic radicals of between 1 and 25 carbon atoms.

11. A composition of matter as set forth in claim 8 wherein said organic radicals are selected from the group consisting of aliphatic, cycloaliphatic, arylalkyl, and aromatic radicals.

12. A composition of matter as set forth in claim 8 wherein said organic radicals contain a heteroatom, said heteroatom being joined to said B-diketone through at least one carbon atom.

13. A composition of matter as set forth in claim 8 wherein said B-diketone is present in an amount between about 0.0005% and about 5.0% by weight based on the weight of said prepolymer.

14. A composition of matter as set forth in claim 8 wherein said fl-diketone is present in an amount of between about 0.002% and about 0.2% by weight based on the weight of said prepolymer.

References Cited UNITED STATES PATENTS 12/1968 Polestak DONALD E. CZAJA, Primary Examiner M. J. WELSH, Assistant Examiner US. Cl. X.R. 

